arXiv subjects

Satoshi Fujimoto

Publications and source records attributed to Satoshi Fujimoto.

101 records · Page 6Linked to original sources

arXiv1999

Spin transport properties of the quantum one-dimensional non-linear sigma model : an application to Haldane gap systems

Spin transport properties of the quantum one-dimensional non-linear sigma model are studied based upon the Bethe ansatz exact solution for the O(3) sigma model and the 1/N-expansion approach for the O(N) sigma model. It is shown that the spin transport at finite temperatures is ballistic and there is no spin diffusion in this system. A possible mechanism for the spin diffusion observed in the NMR experiment of the Haldane gap system AgVP_2S_6 by Takigawa et al. [Phys. Rev. Lett.{\bf 76}, 2173 (1996)] is also discussed. The inclusion of the spin-phonon interaction accounts for the experimental results qualitatively.

cond-mat.str-el↗

arXiv1997

Exact Drude weight for the one-dimensional Hubbard model at finite temperatures

The Drude weight for the one-dimensional Hubbard model is investigated at finite temperatures by using the Bethe ansatz solution. Evaluating finite-size corrections to the thermodynamic Bethe ansatz equations, we obtain the formula for the Drude weight as the response of the system to an external gauge potential. We perform low-temperature expansions of the Drude weight in the case of half-filling as well as away from half-filling, which clearly distinguish the Mott-insulating state from the metallic state.

cond-mat.str-el↗

arXiv1997

Effects of disorder on two coupled Hubbard chains at half-filling

We investigate the effects of quenched disorder on two chain Hubbard models at half-filling by using bosonization and renormalization group methods. It is found that the sufficiently strong forward scattering due to impurities and the random gauge field, which is generated by impurity backward scattering, destroy the charge gaps as well as the spin gaps. Random backward scattering due to impurities then drives the resulting massless phase to the Anderson localization phase. For intermediate strength of random forward scattering, however, the spin gaps still survive, and only one of the charge gaps is collapsed. In this parameter region, one of the charge degrees of freedom is in the Anderson localized state, while the other one is still in the massive state.

cond-mat.str-el↗

arXiv1997

Bosonization Approach to the One-Dimensional Kondo Lattice Model at Half Filling: Reexamination

Low-energy properties of the one-dimensional Kondo lattice model are investigated by using bosonization and renormalization group methods. The formation of the spin and charge excitation gaps at half-filling is discussed in detail both for antiferromagnetic and ferromagnetic Kondo couplings. Also, the effect of the interaction between conduction electrons on the gap formation is studied both for the Kondo insulating phase and for the Haldane gap phase. It is found that while the repulsive interaction changes the dependence of the excitation gap on the Kondo exchange coupling, the attractive interaction can drive the Kondo (or Haldane) insulating phase to a completely different phase of massless metallic states.

cond-mat.str-el↗

arXiv1996

Magnetic and Critical Properties of Alternating Spin Chain with S=1/2,1 in Magnetic Fields

We study an integrable spin chain with an alternating array of spins S=1/2, 1 in external magnetic fields using the Bethe ansatz exact solution. The calculated magnetization possesses a cusp structure at a critical magnetic field H=H_{C}, at which the specific heat shows a divergence property. We also calculate finite-size corrections to the energy spectrum, and obtain the critical exponents of correlation functions with the use of conformal field theory (CFT). Low-energy properties of the model are described by two c=1 U(1) CFTs in H H_{C}.

cond-mat.stat-mech↗

arXiv1996

Effect of Umklapp Scattering on the Conductance in Quantum Wires

We investigate the system-size dependence as well as the temperature dependence of the conductance in 1D electron systems, paying particular attention to the effect of Umklapp scattering. By taking into account the renormalization of the external potential due to electron-electron interaction, the correction to the conductance, 2e^2/h, due to Umklapp scattering is estimated perturbatively. The Tomonaga-Luttinger liquid parameter appears in the conductance via the system-size and temperature dependence.

cond-mat.mes-hall↗

arXiv1996

Competition between the Mott transition and the Anderson localization in 1D disordered interacting electron systems

The competition between the Mott transition and the Anderson localization in one dimensional electron systems is studied based upon the bosonization and the renormalization group method. The beta function is calculated up to the second order in the strength of diagonal disorder by using a replica trick. It is found that the sufficiently strong forward scattering by random impurities destroys the Mott-Hubbard gap, and the backward scattering gives rise to the Anderson localization for the resulting gapless state. On the other hand, if the Umklapp interaction is strong enough, the Mott insulating state still overwhelms the Anderson localization.

cond-mat↗

arXiv1996

Perturbation study on the spin and charge susceptibilities of the two-dimensional Hubbard model

We investigate the spin and charge susceptibilities of the two-dimensional Hubbard model based upon the perturbative calculation in the strength of correlation $U$. For $U$ comparable to a bare bandwidth, the charge susceptibility decreases near the half-filling as hole-doping approaches zero. This behavior suggesting the precursor of the Mott-Hubbard gap formation cannot be obtained without the vertex corrections beyond the random phase approximation. In the low-temperature region, the spin susceptibility deviates from the Curie-Weiss-like law and finally turns to decrease with the decrease of temperature. This spin-gap-like behavior is originating from the van Hove singularity in the density of states.

cond-mat↗

arXiv1996

Comment on ``On the Renormalization of Conductance in Tomonaga-Luttinger Liquid''

Recently Kawabata found that the conductance in Tomonaga-Luttinger (TL) liquids should not be renormalized if one incorporates the renormalization of applied fields correctly. This claim is generalized to include the interactions which carry the large momentum transfer. We thus find that Kawabata's conclusion holds generally for the class of TL liquids. A key observation is that such irrelevant interactions merely renormalize the velocity and the TL parameter at the massless TL fixed point.

cond-mat↗

arXiv1995

Exact finite-size spectrum for the multi-channel Kondo model and Kac-Moody fusion rules

The finite-size spectrum for the multi-channel Kondo model is derived analytically from the exact solution, by mapping the nontrivial Z$_{n}$ part of the Kondo scattering into that for the RSOS model coupled with the impurity. The analysis is performed for the case of $n-2S=1$, where $n$ is the number of channel and $S$ is the impurity spin. The result obtained is in accordance with the Kac-Moody fusion hypothesis proposed by Affleck and Ludwig.

cond-mat↗

arXiv1993

Persistent Currents in Mesoscopic Hubbard Rings with Spin-Orbit Interaction

The effect of spin-orbit interaction on persistent currents in mesoscopic Hubbard rings threaded by an Aharonov-Bohm flux is investigated putting stress on the orbital magnetism. The non-perturbative treatment of the spin-orbit interaction developed by Meir {\em et al.} is combined with the Bethe ansatz solution to deal with this problem exactly. We find that the interplay of spin-orbit interaction and electron-electron interaction plays a crucial role, bringing about some new effects on the orbital magnetism.

cond-mat↗